Experimental Observation of Thin-shell Instability in a Collisionless Plasma
Experimental Observation of Thin-shell Instability in a Collisionless Plasma
复制标题
DOI：
10.3847/2041-8213/834/2/l21
复制
发表时间：
2017-01
期刊：
影响因子：
--
通讯作者：
H. Ahmed;D. Doria;M. Dieckmann;G. Sarri;L. Romagnani;A. Bret;M. Cerchez;A. Giesecke;E. Ianni;S. Kar;M. Notley;R. Prasad;K. Quinn;O. Willi;M. Borghesi
中科院分区：
文献类型：
--
作者：
H. Ahmed;D. Doria;M. Dieckmann;G. Sarri;L. Romagnani;A. Bret;M. Cerchez;A. Giesecke;E. Ianni;S. Kar;M. Notley;R. Prasad;K. Quinn;O. Willi;M. Borghesi
本文报道了激光烧蚀等离子体膨胀到稀薄环境介质中时形成的等离子体壳层不稳定性的实验观察。通过质子射线照相技术，不稳定性的演变在时间和空间上解决的时间尺度比流体动力学的短得多。薄壳的密度超过了周围等离子体的密度，这使得电子向外扩散。双极电场生长在薄壳的两侧，其与密度梯度反平行。薄壳中的波纹导致由该场介导的热压力与由流入的等离子体施加在其上的冲压压力之间的空间变化的平衡。这种不匹配通过驱动流体动力学非线性薄壳不稳定性（NTSI）的相同机制放大了波纹。因此，我们的研究结果构成了第一个实验验证，NTSI可以在碰撞流中发展。
We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.